1. Technical Field
The present invention relates to a method for controlling a wind turbine and to such a wind turbine.
2. Description of the Related Art
Wind turbines are commonly known and an example of a wind turbine is shown in FIG. 1. Such wind turbines are provided for converting energy from the wind into electrical energy and feeding it into an electricity supply grid, referred to hereafter also as an electricity grid or a grid.
Before the wind turbine can feed electrical power into the grid, it must however first be erected and connected to the grid. Once it has been substantially erected, functional tests are often carried out before the turbine can finally be connected to the grid and operated as part of it. During this time, the turbine, which may otherwise have already been completely erected, cannot be operated normally, and in general cannot be operated at all. Depending on where it is sited, there is a risk of the wind turbine cooling down and moisture, in particular from the air, being deposited. There is also a risk that the wind turbine is exposed to moisture from rain too. Although, once it has been erected, a wind turbine is often essentially provided with an enclosed nacelle and an enclosed mast, rain may nevertheless penetrate through ventilation holes, for example, through which it cannot penetrate when the turbine is running because of the flow of ventilation air flowing out. Unfavorable orientation of the wind turbine, in particular of a wind turbine nacelle, can also favor the penetration of rain.
In order to obviate this problem, such ventilation slits can be closed or sensitive turbine parts can be covered or shrouded. However, such measures entail a high cost and there is a risk that such covers or shrouds cannot be removed or cannot be removed completely when the turbine ultimately goes into operation. The erection as well as any functional tests are made harder.
Alternatively, in order to prevent damage from moisture that is deposited or penetrates, heating and/or air-drying can be provided using a corresponding device. Alternatively, attempts may simply be made to make the turbine ready and connect it to the grid as quickly as possible. Where possible, attempts may also be made to erect the turbine in less critical weather conditions but this is often impractical.
Sometimes wind turbines are completely erected and could be connected to the grid but this is not possible for the time being because the grid or a corresponding branch to the wind turbine does not exist yet. Approval for connection of the wind turbine or provision of a corresponding grid branch for the connection may be slow in coming through. In this case, it would be impossible or difficult to operate a heating device and/or drying device when there is no connection to the grid. Connection to the grid is namely often required not only for feeding electrical power from the wind turbine into the grid but also for providing electrical power from the grid for starting up the wind turbine and/or operating turbine equipment. When there is no connection to the grid, the wind turbine can thus not be operated and there is a risk, as described, of moisture being deposited or penetrating, which can sometimes very rapidly result in damage to parts of the turbine, in particular to electrical equipment of the turbine.
The German patent and trademark office has identified the following prior art in the priority application: US 2010/0013224 A1, US 2012/0056425 A1 and U.S. Pat. No. 7,394,166 B2.